Answer:
t = ln(0.5)/-r
Step-by-step explanation:
The decay rate parameter is missing. I will assume a value of 4% per day.
The exponential decay is modeled by the following equation:
A = A0*e^(-r*t)
where A is the mass after t time (in days), A0 is the initial mass and r is the rate (as a decimal).
At half-life A = A0/2, then:
A0/2 = A0*e^(-0.04*t)
0.5 = e^(-0.04*t)
ln(0.5) = -0.04*t
t = ln(0.5)/-0.04
t = 17.33 days
In general the half-life time is:
t = ln(0.5)/-r
